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All samples were submitted for analysis of sulfate, TDS, radium 226, and radium 228. The <br />results of these analyses are discussed in the following sections. <br />General Chemistry <br />General chemistry parameters do not have primary health based standards. TDS has a <br />secondary drinking water standard of 500 mg/L. Sulfate has a secondary standard of 250 <br />mg/L. As shown in Table 2, TDS and sulfate concentrations in all three downgradient <br />alluvial compliance wells have exceeded the 500 mg/L and 250 mg/L secondary domestic <br />drinking water standard in each of the sampling events since 2003. Excess sulfate in <br />drinking water may have negative aesthetic impacts such as laxative effects. High TDS <br />waters are typically hard and have poor quality for drinking. None of the sulfate results <br />exceeded the State Numeric Protection Level of 1,950 mg/L for the GCC site. <br />TDS concentrations from the March, 20, 2012 event ranged from 2,150 mg/L to 3,650 <br />mg/L. TDS concentration exceeded the State NPL of 2,630 mg/L in wells MW -03 (3,060 <br />mg/L) and MW -04 (2,640 mg/L). These are the same wells that caused exceedences in <br />October 2011 event. Figure 2 shows the results of the TDS analyses for all three wells <br />since TDS sampling started in March 2008. <br />The DRMS sent a letter to GCC dated December 8, 2009. The letter presented NPLs for <br />groundwater monitoring for four parameters (TDS, Sulfate, Radium 226, and Radium 228). <br />DRMS generally selected the historic maximum concentration prior to May 2009 as the <br />numeric standard for each of the four parameters. Tables 1 and 2 each list the DRMS NPLs <br />for the four constituents of concern. The letter also described an approach for evaluation of <br />potential of exceedences, and subsequent actions, based on results from the groundwater <br />monitoring program. The following approach was presented. <br />"Sampling for each well will be conducted semi annually and results to be submitted <br />annually. If an upward trend above the set limits is noted, the frequency of sampling will <br />increase to quarterly. If the upward trend still continues, the frequency of sampling will be <br />conducted monthly. If two consecutive monthly samplings still show an upward trend, GCC <br />will present a remedial action to the Division, which will indentify the source of the upward <br />trend and submit the actions GCC proposes to take a receive written approval from the <br />Division." <br />Prior to the current March 20, 2012 sampling, TDS results have not defined an upward <br />trend. As shown in Figure 2, all three downgradient alluvial wells have increasing TDS <br />concentrations for the recent two sampling events, relative to the low concentration <br />reported from the April 2011 sampling event. The same pattern is also noted for the sulfate <br />chart, though no sulfate results exceed NPLs. Prior to April 2011, TDS and sulfate results <br />were characterized by alternating highs and lows that were likely associated with seasonal <br />groundwater fluctuations. Recent TDS highs have been recorded during October sampling <br />events that have followed dry summers with little fall precipitation. Low groundwater <br />levels may tend to concentrate dissolved chemical species, raising the level of TDS. GCC <br />expected to see TDS concentration decrease in the current spring event. However, winter <br />4 <br />